Selsyn apparatus for navigational systems



July 22, 1952 DUGGAR 2,604,529

SELSYN APPARATUS FOR NAVIGATIONAL SYSTEMS Original Filed March 5, 1945 3Sheets-Sheet 1 Heme/502 6f fizgjar July 22, G DUGGAR SELSYN APPARATUSFOR NAVIGATIONAL SYSTEMS Original Filed March 5, 1945 3 Sheets-Sheet 2Llewel/yn G. fizz/53a?" ATTORNEY July 22, 1952 L. G. DUGGAR 2,604,529

SELSYN APPARATUS FOR NAVIGATIONAL SYSTEMS Original Filed March 5, 1945 3Sheets-Sheet 5 Fig. 5.

hml Hil llvllxl r 44 fix 2 7 gjmvg Patented July 22, 1952 UNITED STATESPATENT OFFICE SELSYN APPARATUS FOR NAVIGATIONAL SYSTEMS Llewellyn G.Duggar, United States Army (Granted under the act of March 3, 1883, asamended April 30, 1928; 370 O. G. 757) 7 Claims.

This application is a division of my prior application, SerialNo..581,012, filed March '5, 1945,for Navigational System, now Patent2,482,105, issued September 20, 1949.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment to me ofany royalty thereon.

This invention relates to navigational systems and more particularly tovisual aid devices in which there is obtained a graphic and continuousrepresentation of the position of a craft in relation to knownsurrounding terrain, responsive to signals radiated from two .or moresources of radiant energy at known fixed locations on the terrain. Thespecific embodiment of the invention is intended to be utilized in thekind of system disclosed in the above named prior application,

and to overcome objections to, or add desirable functions in, suchapparatus previously known.

The invention has certain objects stated in said prior application, andaims to aid in the attainment of certain objects of t e improved s stemclaimed in that application.

It isa particular aim to present an embodiment of apparatus which willbe light, compact, and accurate, and which may be constructed at aminimum of expense, with a minimum liability of derangement incident toits normal use and which also may be readily maintained at low cost.

These and other objects and advantages will be readily apparent when thefollowing specification is read in connection with the accompanyingdrawings in which:

Fig. 1 is a diagrammatic layout of my invention.

Fig. 2 is a front View of the indicating portion of my invention,showing the normal condition of the indicator when the device is not inaction, the hoods Bl over the reflectors 83 being omitted.

Fig. 3 is a view of the indicating instrument as illustrated in Fig. '2showing the position of the indicator when the craftis on an azimuthbearing of 315 from one radio station and 230 from the other .radiostation, the azimuth bearing of the axis line between the two radiostations being 30.

Fig. 4 is a view of the indicating instrument as illustrated in Fig. 2in which the indicator beams show 'a position of 120 azimuth for theaxis line between the two radio stations with the craft on an azimuth of350 with one station and 310 from the other station.

Fig. 5 is a view of the indicating instrument illustrated in Fig. 2 withthe cover removed.

Fig. 6 is a fragmentary cross-sectional view along the line 6-6 of Fig.2.

Fig. 7 is a detailed view partly in section of the Sels'yn indicatorlight transmitting means.

Fig. 7a is a plan of the slotted screen in the light transmitting meansof Fig. 7.

Fig. 8 is a fragmentary elevation of the light beam reflector elementfrom the left of Fig. 7.

' Due to the fact that the device known by the trade-mark name Selsynwas used in the embodiment of the invention disclosed herein, that namehas been applied to the elements so involved in the disclosure, as ageneric designation, as defined in my said patent.

Referring to Fig. 1, which illustrates a diagrammatic layout of myinvention, it is seen that the reference numerals l0 and Illa refer toradio direction finder loop antennas of the type which'are normallyautomatically rotated but may be hand rotated to various positions ofazimuth. ThelloOp antennas l9 and [0a are each .utilized with a radioreceiver R and Ba respectively whereby a bearing may be taken on oneor'more radio transmitters in a manner well known in the art. Since theparticular structures of the antenna and of the radio receiver portionof the radio direction finder form no novel part of my invention, nodetailed description thereof is given.

A pair of generator or transmitter Selsyns l2 and i241, each having arotor 13, |3a and a stator I4, M respectively, are so positioned withrespect to each rotating loop antenna I0 and Illa that the loop antenna20 is connected by a drive H (in this case a rotating mast or shaft)with the rotor iii of the generator or transmitting Selsyn I2, and theloop antenna [0a is similarly connected by a shaft of a drive Ila to therotor 13a of the Selsyn l2a. Thus the rotation of the'loop antenna Illwill. cause the generator Selsyn rotor iii to assume the identicalangular position for azimuth. Ina similar manner the Selsyn rotor l3awill have the same angular position of azimuth as the loop antenna I011.

The drives it and Ha may be direct mechanical drives, or, an electricaltranslating device such as a Selsyn may be utilized to transfer therotational movement of the loop antenna to the rotor [3 or Bar of thetransmitting Selsyn.

The stator I4 of the transmitting Selsyn I2 is not fixed but is mountedfor rotation in either direction about an axis identical with that ofthe rotor 13.

In line with the generator Selsyn l2 there is positioned alargeheavy-duty motor Selsyn l6, having a rotor l1 and a fixed stator IS. Thestator I4 of the generator Selsyn I2 is connected by means of a drive I5 to the rotor ll of the fixed heavy-duty motor Selsyn IS. The stator 18of the heavy-duty motor Selsyn l6 remains fixed relative to its support,and the latter is rigidly fixed with the body of the craft. In a likemanner the stator Ma of the generator Selsyn l2a is connected by meansof a drive a to rotor Ila of a large heavy-duty motor Selsyn 16a, havinga fixed stator ltd. Here again the drives [5 and l5a may be directmechanical drives, or, electrical translating devices such as Selsynsmay be utilized to transfer the rotational movement of the rotors ll andIla to the stators I4 and Ma respectively.

The field windings of the stator 18 and of the stator lBa are acted uponby the electrical output of a gyro flux gate compass 19 which isamplified in a torque amplifier 20 and fed commonly into the windings ofeach stator l8 and l8a. The gyro fiux gate compass l9 and the torqueamplifier 20 are of the type well known in the art in which thedirection or heading of a craft is compared with a true north bearing orazimuth.

A compact visual dial instrument D, having two indicating Selsyns 2| and22, Fig. 1, which will be described in more detail later, if situated insuch a position in the craft as to be freely visible and accessible tothe pilot or operator of a craft.

The indicating Selsyns 2| and 22 are of the conventional type having astator 23, and a rotor 24 and 26, respectively. The stator [4 of thegenerator Selsyn I2 is connected in the usual manner to the stator 23 ofthe indicating Selsyn 2!. Similarly, the stator [4a of the generatorSelsyn I2a is connected to the stator 25 of the indicating Selsyn 22.Thus, the rotor 24 will assume the same bearing or azimuth of thegenerator Selsyn rotor l3 and loop [0 and the rotor 26 willindependently assume the azimuth position of the rotor 13a and loopIlla.

By means of the construction related in the foregoing paragraphs, it isseen that the windings of the generator Selsyn stators l4 and I 4a areaffected not only electrically by the position of the rotors l3 and l3aand their antenna loops,

but are also affected positionally by changes in azimuth of the Selsynrotors i1 and Ila respectively. Thus the voltages fed into the stators23 and 25 of the indicating Selsyns 21' and 22 are indicative not onlyof the positions of the rotors I3 and Mia respectively but also areindicative of the angular positions of the generator Selsyn stators l4and Ma respectively, the generator stators l4 and [4a being in turndependent for their angular position upon the position of the rotors I!and Ila respectively of the heavy-duty Selsyns l5 and Mia.

Referring to Figure 2, which is a. front View of the visual indicatingportion of my invention (corresponding to the dial instrument Dschematically shown in Fig. 1) which may be so situated or positioned ina craft that it is capable of easy visual access by the pilot oroperator thereof, it is seen that the reference numeral 21 refers to abezel plate which may be mounted upon a dash or instrument board bymeans of screws 28. A large circular dial or plat 29 having azimuthindicia 30 is so mounted as to permit rotation thereof to variousangular positions. A pointer 3| upon the bezel 2! serves to give theangular position of the dial 29 as it is rotated to various positions.In the center of the large dial 29 a slender marker line 32 havingarrows 33 and 34 is formed through its pivot axis 35 which will furtherindicate the azimuth of a, base line con necting the two radio stationsutilized for obtaining a fix, as will be disclosed more fully later.

To the left of the dial pivot axis 35 in Fig. 2 there is situated aSelsyn azimuth indicating card,

36 having azimuth markings 31 thereon. A reflected light source 38 whichis rotated to various angular positions by an indicator Selsyn (as 22 inFig. 1, not shown in Fig. 2) produces a beam of light 39. Similarly, tothe right of the dial pivot axis 35 there is placed a Selsyn azimuthindicator card 40 having azimuth markings 4i thereon. A reflected lightsource 42 which may be rotated to various angular positions by anindicator Selsyn (as, 2| in Fig. 1, not shown in Fig. 2) produces a beamof light 43.

Referring to Fig. 5 which is a front view of the indicator portion of myinvention with the dial 29 removed, it is seen that the referencenumeral 44 refers to a center spindle fixed with the bezel 21, havingmounted thereon a fixed central gear 46 held in position by a spindlenut 45. A support member 41 in the form of a cross beam diametricallyarranged behind the dial 29, carries bolted thereto at 86 a cylindricalbase ring gear 48 co extensive with the dial having external spur teeth49 out along the lower of its perimeter. The support member 41 has a hubrevoluble upon the fixed spindle 44 to permit rotation of thecylindrical ring gear 48 about the fixed spindle 44. Rotation of thegear ring 43 is accomplished by means of a small gear 51 mounted upon ahand knob 50 at the lower side of the apparatus.

To the left of the fixed gear 46 and meshing therewith is mounted on thecross-beam 41 an idler gear 52 mounted upon a stud shaft 53 by means ofa spindle nut 54. To the left of the idler gear 52 and meshing therewithis a driven gear 55 having the same diameter as the fixed gear 46.

Similarly, to the right of the fixed gear 46 and meshing therewith is anidler gear 56 rotatably mounted upon a spindle bolt 51 and held theretoby the bolt head 58. To the right of the idler gear 56 and meshingtherewith is a driven gear 59 having the same diameter as the fixinggear 46.

Rotation of the knob 50 rotates gear 48 about the spindle 44, carryingwith it the cross-beam 41 and due to the two idler gears 52 and 56meshing with the fixed gear 46, the two driven gears 55 and 59 arethereby oppositely rotated through an angle equal to that of the angularrotation of the ring gear 48. The dial 29 (Fig. 2) is fixed upon thering gear 48 so that rotation of the latter rotates the dial 29 equally.The Selsyn indicator card 36 is mounted upon the driven gear 55 so as torotate directly therewith. In a similar fashion the Selsyn indicatorcard 40 is mounted directly upon the driven gear 59 so as to rotatedirectly therewith. By the functioningof the idler gears, the gears 55and 59 are rotated on the cross-beam 41 exactly enough to keep them andtheir cards, dials 36 and 40 oriented constantly in one relation to thedirection of the pointer 3|, although the reflectors 38 and 42 may bevariously positioned on the same axis.

Referring to Fig. 6, it is seen that the reference numeral 60 refers toa casing in which the instrument is housed. The indicating instrumentmay be mounted in any suitable manner, as, for example, upon theinstrument board of a craft or vehicle. Extending normally from the backwall of the casing is the stationary spindle 44, its foot flangefastened to said Wall by bolts 61 and 62. Secured to the base of the hubof the cross beam 47 around the spindle 44 there is a rotating armbracket 63 held on the hub by bolts 64 and 65. A right angle extension66 of the bracket 63 contains an integral light bulb socket 61 in whichis placed a small light bulb 68. .An insulated spring contact member 69serves to engage the center contact of thelight, bulb whilethe circuitis completed convention-.-

ally through the bracket, current being delivered through a cable 10. Aconcave rrefiec'tor'll :refleets the light downwardly from" the bulbthrougha set of condensing and collimating lenses", which-are mountedupon an arm 13 of the bracket 63. y The stator-23 of'indicator Selsyn2lis mounted' uponthe base blocks HI-15, attached to an elongated tubularhub of the gear 59 so that the latter may rotate the stator, and serveasa bushing in the support 41 for the light tube 18 to be described. Ballbearings 16 are. provided between the rotor 24 and hub of gear59.Electrical connections are made to the indicator Selsyn rotor 24 bymeans of brushes '1! and IT which are mounted upon the rotating armbracket 63, one of which at least should be insulated. The leads tothese brushes may be conventional and are not shown. I Passing throughthe center of the indicator Selsyn rotor and stator and securelyattached to the rotor 24 there is a light conducting tube or shaft vl8the extreme .lower end of which is broadened out to a shoulder 19 whichrides upon the lower ball bearings 80. Mounted on the same end ofthetube as the shoulder wand at right angles to the tube 18 there isaxhoodor housing 8| having a slotted screen 82 Fig; v'l) communicatingwith the interior of the tube 78. A reflector 83 mounted'within the hood8| serves to direct a narrow beam of light across the .face of the dialor plat '29 from the beam oflight passing downwardly through the. tube18 and narrowed by the slotted screen 82. See Figures 7 and 7A. Sincethe tube 18 isfastened to the indicator Selsyn rotor 24 and rotatestherewith, it is seen that rotation of the indicatorSelsyn rotor 24 willcause the beam of light which is reflected from Within the'tubularhousing 8| to be angularlyrotated an amount equal to. theangular rotation of the indicator Selsyn rotor 24; The direction of thelight beam issuing from the light conducting tube or shaft 18 may bechanged by means other than that illustrated; for-example, the reflector83 may be replaced by a prism or by amirror arrangement.

The dial 29 is mounted by means of acover stud 84 screwed therethroughinto the idler gear pivot 51 on the cross-member 41.

The dial 29 is formed with circular openings concentric with the axes ofthe gears 55 and 59,

to, receive hubs of these gears therethrough hav ing end faces set justbeyond'the face of the dial, and the cards36 and 40 are secured to theserend faces of the hubs by screws as at-85 in Fig.6, so that the cardslie in close parallel relation" to the dial 29. The structureof theSelsyn indicating mechanism 22 is'identical with that of the Selsynindicator mechanism 2| as illustrated in Figure 6. The face or theentire indicating instrument is protected by a cover glass 81. Each tube18 and reflector 83 being fixed with the rotor of the adjacent Selsyn,the light beam thus assumes an angular position over the dial whichcorresponds to the induced angular position of the stator thereby thecombined radio beam input from l0 or we and from the gyro flux gatecompass, plus or minus the movement put in by knob 50 manually. Thelatter may be clockwise or counterclockwise, according tothe instantangular position of the eraft's longitudinal axis in relation tolongitude lines on the earth, and so thebase line 32 will vary from'itsinitial normalrelation to theradiusof pointer 3! shown in Fig..

2- bythe value of input fromtknob 50. .Without rotation of the knob, thecombined input from the antenna [0 or 10a and gym. flux'coxnpass tendsto introduce an error-into the angular position of the beams 39 and43requal'to the angular value of the input from the gyro flux compass,but the operation of'the knob 50 to position the ring gear inrelation'to pointer 31 according to the true north angle derived eitherfrom a compass. indicator or as above stated by computation from theknown positions of the. two ground stations in relation to true north,has the effect of subtracting. angular movement error produced by theinduction values derived from Selsyns l6 and l6a' in the electricalinput to the I Selsyns 22 or 2|. Consequently the geographical positionsof the radio beams tuned in at the antennas l0-l0a.then become definedon'the plat by the light beams 39 and 4.3; the relations of thelight'beams mutually and their relations to the actual radio beams haveto each other and to a line on the earth between the two land stationswhere the radio beams originate. laid over or formed-at the dial 29 on ascale which brings the points on-the map representing the stationsontheaxes of the cards 36 and 40, the light beams 39 and 43 .then have thesame positions on the map which the radio beams from the land stationshave inrelation to the earth. The intersection of the beams Hand 43gives a fix representing the location of a .point on the map or inrelation to the line 32 which corresponds to the position of the craftoverthe earth.

A modification of. the indicating instrument just described may be hadby providing a transparent map overlying the cover-glass 81, so that thepilot of a craft may actually mark his course on the map and so guidethe craft that-the in-, tersection of the two light beams falls upon themarked course. Instead'of providing a. transparent map overlay, theimage of a map may. be projected upon the .oover glass. I By properspacing of the projector, the scale of the map may be varied. A stillfurther modification may be had in the provision of a fluorescentcoating upon the inside of the cover glass 81 whichwill be excited byultraviolet light emitted instead of the visible light source described.

To use the device, the radio antennae direction finders l0 and IDA areeach rotated in the conventional manner and trained upon two known radiostations or beacons. The thumb screw on; the visual position indicatoris then turnedso that an indicated azimuth between the two light beamindicators 38 and 42 corresponds to that of the true north azimuth knownto exist between the, two ground radio stations or beacons beingutilized. In this manner a similar triangle is established on the faceof the indicating instrument which may be compared to the triangle drawnon a map showing the location of the two radio stations or beacons beingused. The point of intersection of the two light beams 39 and 43 willshow the position :of the craft at-all times. Furthermore, the scale ofthe instrument depends upon the proportion of the distance between theaxes of the Selsyn indicators to the distance between the two radiostations or beacons. I

Figure 3 illustrates the appearance of the dial of the indicatinginstrument when the base line connecting the two radio stations orbeacons has If a map is an azimuth bearing of 30 and where the craft ison an azimuth bearing of 315 from one radio station or beacon and on anazimuth bearing of 230 from the other radio station or beacon. Theintersectionof the two light beams indicates the position of the craftwith respect to the two radio stations or beams.

Figure 4 illustrates the appearance of the indicating instrument whenthe base line between the two radio stations or beacons has an azimuth 1bearing of 120 and where the craft lies on an azimuth of 350 from one ofthe radio stations and on an azimuth of 310 from the other of the radiostations.

Although I have illustrated one embodiment of my invention, it isobvious that many changes may be made without departing from theinvention as defined by the appended claims.

I claim:

1. A visual indicating apparatus for use in a navigational system of thecharacter described, a cylindrical ring having gear teeth onsubstantially half of its periphery, a support member bridging saidcylindrical ring and rigidly secured thereto, a fixed gear positioned inthe center of said support member, a pair of idler gears rotatablymounted on said support member and meshed with said fixed gear, a pairof driven planetary gears rotatably mounted on said support member andmeshed with said idler gears; said fixed gear and driven gears all beingof like diameter, means to rotate the ring to conform to given anglevariables, a Selsyn stator fixed with each driven gear, a Selsyn rotorcperatively associated therewith, and a radial indicator device carriedby the rotor.

2. A visual indicating device for a navigational system of the characterdescribed, comprisin a cylindrical outer ring member, a support memberdiametrically bridging said ring member and secured thereto, a centershaft about which said cylindrical ring may rotate, a fixed gear uponsaid shaft and mounted in the center of said support member, a pair ofidler gears oppositely located on said support member and meshing withsaid fixed gear, a driven gear outwardly of and meshed with each of saididler gears and rotatably mounted upon said support member; said fixedgear and driven gears having the same diameter, a Selsyn indicatorhaving a rotor and a stator located coaxially with each of said drivengears and mounted on said support member, means for forming a radialbeam of light from the rotor of each of said Selsyn indicators wherebysaid beam of light indicates the angular position of said indicatorSelsyn rotor.

3. A visual direction indicating device for charts in a navigationalsystem, comprising a stationary body including a center shaft, a supportmember rotatably mounted on said shaft, a Selsyn having a rotor and astator, said stator mounted revolubly on said support member on an axisparallel to said shaft, a light conductin tube fixed with the rotor andpassing centrally through said rotor and stator, a light source carriedby said support at one end of the tube, a light reflecting housing atthe opposite end of said tube for reflecting a beam of light radiallyfrom said tube across and toward a plane normal to the center shaftaxis, a surface plat at said plane, and means for rotating said supportmember, and operative connections between said stationary part and saidsupport responsive to rotation of the latter on said center shaft toorient the said stator directionally in a predetermined relation to saidstationary body throughout said rotation of said support.

4. A visual direction indication device for defining a transient lineacross a plat surface in a navigational system of the characterdescribed, comprising a stationary body including a center shaft, a platsupport revolubly mounted in a plane normal to the shaft for rotationaround .the shaft in said plane, a stationary center gear on the shaftadjacent said support, a pair of planetary gears of the same diameter assaid center gear revolubly mounted at opposite parts of said support,respective idler gears revoluble on said support meshed with the centergear and the respective planetary gears, a Selsyn for each planetarygear having a stator coaxial with and fixed with the planetary gearspaced from said plane, and having a concentric rotor, an axial memberextended from the rotor through the planetary gear and beyond saidplane, means including said extension to form a light beam from therotor axis without said plane and theretoward and along the plane so asto illuminate a line area on the surface of a plat surface when mountedon said support, a base gear on said support concentric with the centershaft, and means to drive said gear alternatively in oppositedirections.

5. The structure of claim 4 wherein said'means to form a. light beamincludes a light source on the axis of the planetary gear remote fromthe said plane, said extension from the rotor being a light conductingshaft fixed with the rotor extending revolubly through the planetarygear and said plane a distance, and a reflector fixed on the extensionconstructed to reflect a beam inwardly toward and along the plane adistance.

6. The structure of claim 5 including a plat surface fixed with saidsuppart substantially coincident with said plane, a base gear fixed withthe support concentric with said center shaft, a pinion on said bodymeshed with the base gear, means to operate the pinion alternatively inopposite directions, and an indicator card fixed on each planetary geararound said light conducting shaft closely over said plat surface, eachcard being characterized to indicate its angular movement around itsaxis relatively to said support and plat.

'7. The invention of claim 6 in which said plat surface is marked with abase line coincident with the axes of the said cards, each card beingcircular and formed with a peripheral scale of degrees azimuth, thezeros of both scales being coincident with a predetermined ermanentdirection.

LLEWELLYN G. DUGGAR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,972,889 Hayes Sept. 11, 19342,027,528 Hammond Jan. 14, 1936 2,127,415 Marique Aug. 16, 19382,299,083 Elm Oct. 20, 1942 2,361,956 Mosely Nov. 7, 1944 2,433,860McDowell Jan. 6, 1948

